Typically, for an operation of a mobile terminal, the mobile terminal needs to be supplied with power. To this end, a battery is mounted on the mobile terminal, and is typically charged by a charger. With respect to such a charging scheme, in order to support the portability of the mobile terminal, research has been performed on a non-contact scheme, a wireless charging scheme, or the like.
In such a wireless charging scheme, when a resonance condition coincides between the mobile terminal to be charged and a charging device which charges the mobile terminal, power delivery efficiency is maximized. Also, in the case of power delivery, it is ideal that the amount of transmission power coincides with that of reception power. However, due to various kinds of external factors occurring along a power delivery path, the amount of reception power is forced to be smaller than that of transmission power.
Accordingly, when a power reception state of the mobile terminal is capable of being identified and a resonance frequency for the generation of transmission power by the charging device is capable of being adaptively adjusted based on the power state information, power delivery efficiency can be maximized. To this end, the mobile terminal transmits power state information on power, that the mobile terminal receives, to the charging device while power is being transmitted between the mobile terminal and the charging device. Then, the charging device determines the amount of power based on the received power state information, and transmits power to the mobile terminal.